点击Jbutton使JPanel消失

Question

我有两个JPanel的问题。两者都用一个绿色矩形表示，一个比另一个大。我一直在尝试从一个面板切换到另一个面板，这意味着，当你单击按钮时，一个面板会替换框架中的另一个。然而，我找不到第二个出现的解决方案。我得到的最多的就是第一次躲藏。我应该如何集中注意力？我没有主意了。

public class GrowAndShrinkSquareGUI {
    JFrame frame;
    SquareDrawPanel greenPanel;
    public class SquareDrawPanel extends JPanel {
        int locationX;
        int locationY;
        int width;
        int height;
        SquareDrawPanel(int x, int y, int w, int h) {
            locationX = x;
            locationY = y;
            width = w;
            height = h;
        }
        public void paintComponent(Graphics g) {
            g.setColor(Color.green);
            g.fillRect(locationX, locationY, width, height);
        }
    }
    public class growAndShrinkListener implements ActionListener {
        JButton button;
        public growAndShrinkListener() {
            JButton button = new JButton("Click me to grow the Square");
            frame.add(button, BorderLayout.NORTH);
            button.addActionListener(this);
        }
        @Override
        public void actionPerformed(ActionEvent e) {
            System.out.print("clicked");        
            greenPanel.setVisible(false);
        }
    }
    public static void main(String[] args) {
        GrowAndShrinkSquareGUI test = new GrowAndShrinkSquareGUI();
        test.go();
    }
    public void go() {
        frame = new JFrame();
        frame.setSize(500, 500);
        frame.setVisible(true);
        frame.setLayout(new BorderLayout());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        drawPanel(greenPanel);
        growAndShrinkListener button = new growAndShrinkListener();
        //addButton(CreateJButton());
    }
    private JPanel createRectPanel(int x, int y) {
        greenPanel = new SquareDrawPanel(x, y, 100, 100);
        return greenPanel;
    }
    private void drawPanel(JPanel panel) {
        panel = createRectPanel(setLocationX(), setLocationY());
        frame.add(panel, BorderLayout.CENTER); // DoesNot run properly
    }
    private int setLocationX() {
        int centeredX = frame.getWidth() / 2 - 50;
        return centeredX;
    }
    private int setLocationY() {
        int centeredY = frame.getHeight() / 2 - 75;
        return centeredY;
    }
}

Answer 1

对于这个特定的任务，您应该使用CardLayout，它使您能够在"卡"之间快速切换。卡本质上是与一个名称相关联的JComponent：

public class GrowAndShrinkSquareGUI {
    CardLayout layout;
    JPanel cardPanel; // Holds the cards
    public class SquareDrawPanel extends JPanel {
        int locationX;
        int locationY;
        int width;
        int height;
        SquareDrawPanel(int x, int y, int w, int h) {
            locationX = x;
            locationY = y;
            width = w;
            height = h;
        }
        public void paintComponent(Graphics g) {
            g.setColor(Color.green);
            g.fillRect(locationX, locationY, width, height);
        }
    }
    public static void main(String[] args) {
        GrowAndShrinkSquareGUI test = new GrowAndShrinkSquareGUI();
        test.go();
    }
    public void go() {
        JFrame frame = new JFrame();
        frame.setSize(500, 500);
        frame.setVisible(true);
        frame.setLayout(new BorderLayout());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        // Set up CardLayout
        layout = new CardLayout();
        // Set up the first panel
        JPanel firstPanel = new JPanel(new BorderLayout());
        JButton switchButton = new JButton("Switch to green panel!");
        switchButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {
                layout.show(cardPanel, "green");
            }
        }
        firstPanel.add(switchButton, BorderLayout.NORTH);
        layout.add(firstPanel, "first");
        // Set up the second panel
        JPanel secondPanel = new SquareDrawPanel(5, 5, 50, 50);
        layout.add(secondPanel, "green");
        // Set up the main panel
        cardPanel = new JPanel(layout);
        frame.add(cardPanel);
    }
    private int setLocationX() {
        int centeredX = frame.getWidth() / 2 - 50;
        return centeredX;
    }
    private int setLocationY() {
        int centeredY = frame.getHeight() / 2 - 75;
        return centeredY;
    }
}